Cooling jackets provide an excellent means for cooling electric motors and generators, such as brushless permanent magnet generators operating at high speeds and driven by fuel-powered engines to generate electrical power. Electric motors and generators generate considerable heat and require an efficient cooling system. Motors and generators are often equipped with a means for cooling formed of a cooling jacket provided with grooves or passages built into the motor/generator housing. Circulating oil or water, or even air through the grooves or passages provides cooling to the motors and generators.
It is common practice in machining applications to machine spiral grooves into a metal part. Machined spiral grooves in a housing have been shown to work well to remove the necessary heat from these components, however machined spiral grooves are expensive to cut in a production environment. Further, casting a continuous spiral groove is not simple to achieve nor desirable due to the negative relief caused by the pitch of the spiral, unless parted on several planes, which is a major disadvantage. The several parted planes force the use of multiple parting lines which means more complicated casting procedures and much higher manufacturing costs.
In a United States patent application to Burjes et al. (2007/0268464 A1), a method of making a motor/generator cooling jacket is disclosed. A hollow cylindrical housing is cast with an outer peripheral surface and an annular axially facing end surface, a plurality of grooves formed in the outer peripheral surface and a radial lip at one end. The Burjes et al. patent application also teaches inlet and outlet ports drilled through the end surface to communicate with the grooves, and sealing recesses and O-ring seals integrated for sealing. However, the prior art process does not provide a simple yet effective and efficient method of manufacture.
Specifically, the Burjes et al. application may require separate cores for the cooling jacket in the housing. Separate cores would increase the casting and other manufacturing costs. Further, the Burjes invention teaches a non-continuous flow path, which may require the cooling fluid to make 180-degree turns and flow in opposite directions. This non-continuous circulation path may lead to inconsistent and inefficient means for equally cooling the stator, and may lead to a less efficient system potentially causing a higher than desired pressure drop across the entire path of the fluid.